Studies of chylomicron formation during conditions of impaired protein synthesis are in progress. Acetoxycycloheximide is used to inhibit intestinal protein synthesis in the mesenteric lymph fistula rat and the apoprotein pattern of collected chylomicrons is examined on SDS acrylamide gels. Preliminary results indicate that the synthesis of a rapidly turning over chylomicron apoprotein immunologically related to HDL is impaired during inhibition of protein snthesis. Further studies are in progress to characterize this apoprotein further. Studies of the carbohydrate composition of human and rat serum lipoproteins are in progress. Studies of the glycolipid content of several classes of lipoproteins will be determined for possible differences. A comparison of apoprotein patterns in mesenteric and serum lipoproteins is currently in progress to detect possible differences between the apoproteins of serum and lymph lipoproteins. Ultrastructural localization of chylomicron apoproteins within intestinal epithelial cells using monospecific antisera conjugated to horse radish peroxidase are in progress.